textproduct: Rapid City

KEY MESSAGES

- Isolated high-based showers will develop over the southern Black Hills and southern SD this afternoon.

- Clearer skies and mild temps return for the weekend.

- Chance for showers and thunderstorms Sunday afternoon. Severe weather isn't expected.

UPDATE

Issued at 1034 PM MDT Fri May 1 2026

Looking at things this evening...cold front looks to cross the region from northwest to southeast Saturday afternoon. On the fire weather side of things...this may be a scenario where lowest RHs are realized during the early- to mid-afternoon hours ahead of the front, but may stall or start to recover/increase a bit behind the front as the new airmass and some clouds push through. We did massage the wind/wind gust forecast post-front, mostly to broadbrush the slightly higher NBM speeds out over additional real estate across the northwest South Dakota plains down to about I-90 using ADJMAV. While we have had some recent moisture and some green- up of fuels, the combination of minimum RHs of 15-25% and wind gusts 20-40 MPH will still spell "elevated" fire weather conditions. On the precip side of things...a few CAMs are trying to fire a few showers or even a thunderstorm along the front, but nearly all raw model guidance in addition to blends like ConsShort and the NBM are dry (PoPs generally 10% or less), and spot checking a few model forecast soundings, moisture at the top of the boundary layer along the front seems quite shallow with the low-levels dry. Have thus held with the NBM and kept any mention of precip out of the forecast for now. Better chances still appear to arrive Sunday. No major updates/changes made from Sunday onward.

DISCUSSION

(This Evening Through Friday) Issued at 1251 PM MDT Fri May 1 2026

Most recent water vapor imagery and upper air analysis shows ridge axis extending from ID/MT into northern CA/NV. Meanwhile, an upper low sits over Ontario/Quebec. The Northern Plains sits under north/northwest flow with weak upper wave moving through SD. Recent KUDX scans are picking up on scattered high-based showers over Bennett County, though webcams in that area aren't showing any precip making it to the ground. CAMs also have hinted at showers developing in the convergence zone over the Southern Hills. Have painted light/isolated PoPs for southwestern SD for this afternoon.

Ridge builds into the region through early this weekend, bringing dry and warm conditions to the CWA late tonight into Saturday. Saturday will be warm with highs in the 70s across much of the area. Humidities Saturday afternoon will drop to ~15% across southwestern SD with winds gusting up to ~25 mph. This would put us near or at Red Flag criteria; however, the recent precip and fuels in green up preclude any critical fire weather concerns.

Ridge breaks down by Sunday, bringing northwest flow back to the region. Upper level wave slides southeastward from Canada and grazes the CWA on Sunday. Some showers/storms may develop across the Black Hills and western SD on Sunday afternoon as this wave moves through, though not expecting anything severe. Deterministic guidance in good consensus of a Rex Block developing over the western US for the beginning of next week. This would keep our neck of the woods under unsettled northwest flow with mild temperatures and periodic chances for some light precip as a result.

AVIATION

(For the 06Z TAFS Through 06Z Saturday Night) Issued At 1034 PM MDT Fri May 1 2026

VFR conditions are expected at both TAF sites through the forecast period. A cold front will move in from the NW Saturday afternoon, bringing windy conditions. Precipitation is not expected.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.